PS has things like CAP, OM of the month, STABmons, etc... We need more meta games to make us unique. I say we do free for all but really the choice is yours.
The side metagames we already have are barely played as it is. CAP is literally its own project that's had like half a decade of work. The Side Metagames are hardly a draw to smogon, and all of the side metagames that PO used to have that died indicate they're not a draw to PO either.
I'd rather come up with a handful of good metagames and spend time tiering those, rather than to try tier too many overly gimmicky metagames. Things like STABmons are best relegated to tournaments due to how quickly people lose interest in them.